How to report a possible drug house on my block

Where do I start? I was thinking of calling the local precinct..I'm just not sure what to do.
Everyday throughout the day & night a taxi comes & waits for a few minutes while a person goes in & then comes right back out & leaves. (different people). The lady that lives there had the house up for sale since last year (because she was unable to keep up on her mortgage since her BF was put in jail.) but recently the for sale sign is gone.
Another strange thing....She parks her car a block & 1/2 away so its not in her driveway. (this started a couple of months back).

Re: How to report a possible drug house on my block

Call your local precint and explain your concerns and what you've seen. They will send someone out to watch the house and see what goes on.